A typical drill rig comprises a tower which supports a drill head that in turn rotates a drill string. The drill head can be slid up and down the tower for the purposes of tripping a drill into and out of a hole. The motion of the drill head is controlled by one or more hydraulic rams. The size of the rams used is dependent upon the maximum drilling depth of the drill rig. For relatively shallow holes for example up to 800 m, a drill rig may comprise two rams each having 120 mm (approximate 5″) diameter. Such a drill rig may require a power pack providing approximately 400 hp and consume in the order of 960 L of fuel per day. In comparison, a drill rig designed to drill to a depth of say 2000 m may incorporate two rams each of 300 mm (12″) and require a 2500 hp power pack and consuming approximately 8400 L of fuel per day. The reason that larger rams are required to drill deeper holes is to ensure that the drill rig can apply the required hold back as the weight of the drill string increases with increasing hole depth enabling control the effective weight applied by the drill string to the bit.